Electrostatic focussing-type television picture tube utilizing a plurality of metal disks

ABSTRACT

An electrostatic focussing-type television picture tube wherein a plurality of ring-shaped metal plates are successively coaxially stacked to form an electrode assembly with the plates being separated, a relatively small space between adjacent plates. This electrode assembly is placed between a first accelerating electrode and a screen, whereby a periodic electric field is produced by the electrode assembly to thereby provide a lens effect of a main lens which is apparently a unitary system and which is moreover substantially free of aberration.

United States Patent 1 ,7 2, 5

Nakamura [451 Nov. 14, 1972 ELECTROSTATIC FOCUSSING-TYPE 3,417,199 12/ 1968 Yoshida et a1. ..3 15/ 31 R TELEVISION PICTURE TUBE 2,070,3 l9 2/ 1937 Rudenberg ..3 l 3/ 78 X UTILIZING A PLURALITY OF NIETAL 2,548,870 4/1951 Colterjohn ..3 15/15 X DISKS FOREIGN PATENTS OR APPLICATIONS [72] Invenm" Nakamm" Takatsuk" Japan 74,232 12/1944 Germany ..315/14 [73] Assignee: Matsushita Electronics Corporation,

Osaka, Japan Primary Examiner-Benjamin R. Padgett [22] Filed: April 17, 1970 Assistant Examiner-J. M. Potenza Attorney-Stevens, Davis, Miller & Mosher [21] Appl. No.: 29,519

[57] ABSTRACT [30] Foreign Application Priority Data An electrostatic focussing-type television picture tube 7 V wherein a plurality of ring-shaped metal plates are April 21, 1969 Japan ..44/34362 successively coaxiauy stacked to form an electrode sembly with the plates being separated, a relatively g "315/31 small space between adjacent plates. This electrode assembly is placed between a first accelerating elec- [58] Field of 13/79 3 1 F trode and a screen, whereby a periodic electric field is produced by the electrode assembly to thereby pro- [56] References Cited vide a lens effect of a main lens which is apparently a unitary system and which is moreover substantially UNITED STATES PATENTS free of on- 2,884,559 4/1959 Cooper et al ..3 15/31 TV 3 Claims, 5 Drawing Figures /0 f A 1 &

4 6 i .1 i I n 2 77 7 P 7 I 1 i 1 i i I 3 8 X \I j A V 11/ o-- A $9 6 D E F PATENTEDMV 14 I972 SHEET 1 BF 2 --Vmax 4 INVENTOR ATTORNEY? PATE'NLTEDMM 14 m2 SHEET 2 BF 2 F/GI 5 ELECTROSTATIC FOCUSSING-TYPE TELEVISION PICTURE TUBE UTILIZING A PLURALITY OF METAL DISKS very difficult to employ electrodes having small aperj tu res. Moreover, any attempt to obtain a lens system with a short focal length would result in increased aberration. Furthermore, there has been another drawback in that high precision constituent members were required to provide a main lens system and this conflicted with a general requirement that the use of electrodes manufactured by means of deep drawing be avoided as far as possible.

There has been still another electrostatic focusing method known to the prior art employing a periodic electric field-type lens system. This lens system consisting of a plurality of electron lens each having a relatively long focal length and successively disposed along the path of an electron beam had the advantage that it substantially involved no aberration. In fact, however, this type of electrostatic focusing method has never been applied to any television picture tubes due to the fact that, as far as the convensional arrangements of electrodes were used, it was unavoidable that the arrangement of focusing system electrodes tended to become complicated and moreover the overall length of the electron guns tended to be longer.

The picture tube according to the present invention also incorporates an electrostatic focusing lens system 0 periodic electric field type in which the arrangement of electrodes is a simple one comprising a plurality of ring-shaped metal plates successively stacked with each plate being separated from the succeeding one by a relatively small space, and furthermore the individual lens units providing a periodic electric field interferes with one another so that apparently they act as a unitary main lens system to exert a focusing action on the electron beam.

Still further, the lens effect can be readily adjusted by selecting the diameters of central apertures of the respective ring-shaped metal plates so as to differ from one another.

The other objects, features and effects of the present invention will be apparent from the following detailed descriptions of the preferred embodiments taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a local side cross section of a picture tube embodying the present invention;

FIG. 2 shows an enlarged side cross section of the main lens system incorporated in the picture tube of FIG. 1;

FIG. 3 shows an example of the periodic electric field produced by the main lens system of FIG. 2;

FIG. 4 shows local side cross section of another picture tube embodying the present invention; and

FIG. 5 shows the enlarged side cross section of the main lens system incorporated in the picture tube of FIG. 4.

Referring now particularly to FIG. 1. a glass bulb 1 is provided with a cathode 2, a cup-shaped control grid 3, a first acceleratingelectrode 4, a periodic electric fieldtype electrostatic focusing system 5 and a fluorescent screen 6 which are sealed in this arrangement in the inside of the glass bulb 1. The periodic dlectric field electric focusing system 5 comprises a plurality of ringshaped metal disks 8 each thereof having a circular aperture 7 through which an electron beam is passed and, as shown in FIG. 2, the plates 8 are arranged in a stacked form in the direction of the electron beam path with the disks being spaced away from one another by a distance d. Here, the radius of the aperture 7 is r and the radius of the metal disks 8 is r and the thickness of the metal disks 8 may be about 0.8 mm or smaller.

Of the plurality of the metal disks 8 which are six in all, for example, the metal disks of odd orders and those of even orders are connected to bus bars 9 and 10, respectively, with a group of the odd-ordered metal disks A, C and E being connected to a power source E and a group of the even-ordered metal disks B, D and F to a power source E Potential V of the power source E and potential V of the power source E are so chosen that there is a relation V V 0.2 V and the value of V may be arbitrarily selected to be between 5 KV and 30 KV. A conductive film 11 disposed to extend from the neck portion of the bulb to the internal surface area of its funnel portion is electrically connected to the last electrode F of the focusing system 5.

Assuming that d r, and V %V the potential distribution of a periodic electric field along the axis of the tube takes a wavy form as shown in FIG 3, and the effective values of the maximum potential V and the minimum potential V,,,,,, within the bounds of the paraxis of the electron beam path may be given as V z V +2V )/3 and V,,,,-,, z (2V -l-i V )/3 respectively.

The focusing effect on the electron beam by the focusing system 5 will be greater as the value of V V (V V )/3 increases, and this focusing effect will also be greater as the ratio of the distance d to the radius r of the aperture 7 becomes larger. However if the ratio r d has an excessively large value, it will give rise to a problem of aberration within the focusing system 5.

According to the picture tube of the present invention, there is provided a relation d 2r between the distance d and the aperture radius r,. This limitation is also advantageous from the aspect of arranging the electrodes of the focusing system 5 in a compact form.

According to the present invention, it has also been proved that the provision of a relation d r r among the distance d, the radius r of the metal disk 8 and the aperture radius r has the effect of reducing the influence due to the penetration of external electric fields.

While in the present embodiment both the aperture radii of the metal disks in the odd-ordered group and the metal disks in the even-ordered group are represented by the same r they may assume different values provided that the previously stated conditions are satisfied.

With another embodiment of the present invention as shown in FIGS. 4 and 5, the aperture radius of respective metal disks A, C, E and G' of an odd-ordered group is r;, and that of metal disks B D and F of an even-ordered group is r,,. The values of these radii are so chosen that there is a relation r r Assuming now that there is provided a relation V V with respect to potential V of a power source E and potential V of a power source E in addition to a periodic electric field effect due to the relation V V a periodic electric field effect owing to the relation r r synergetically acts to thereby exert an improved focusing action on the electron beam. In FIG. 4, numeral designates the focusing system.

Further, the tests conducted by the inventor have shown that with the, electrode arrangement of FIG. 5 where r and r are preferably selected, an excellent beam focusing effect as well as a good average beam velocity can be obtained even though the value of V were chosen to be in close proximity to zero volt. In this case, V, may assume any value between 5 KV and 30 KV.

What is claimed is: I. In a picture tube including a periodic electric fieldtype lens system which comprises at least five metal disks having circular apertures and being axially aligned in sequential order from a first accelerating electrode and along an electron beam path between said first accelerating electrode and a fluorescent screen, the group of disks of odd order being at one potential and the group of disks of even order being at another potential so as to form a periodic electric field along said electron beam path, the improvement in that the apertures of the disks of each said group have the same diameter, the aperture radius r of said disks and the distance d between adjacent disks meet the condition 2r; g d, whereby said disks constitute a unitary main focusing lens system under said periodic electric field to cause electron beams passing through said first accelerating electrode to focus on said fluorescent screen.

2. A picture tube according to claim 1, wherein the outer radius r of said disks, the inner radius r of said disks and the distance d between adjacent disks meet the conditions r -r d. V

3. A picture tube according to claim 1, wherein the thickness of each of said disks is less than 0.8 mm.

UNHEB STATES PATENT *iCE I CERTH KATEJ e eeneiic'iien Patent No 702 I 950 Q Dated November 14 1972 Inventofls) HirOtO NAKAMlIRA It is certified that error appears in the above-imptified potent and that said Letters Patent are hereby corrected as S ')Ow11 below:

Please insert the following reference to the Japanese Utility Model missing' from the original Letters Patent:

Japan, Utility Model Application No. 40773/69 filed April 24, 1969.

Also correct the filing date of Japanese Patent Application No, 34362/69 as follows:

April 24, 1969.

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer I Commissioner of Patents FORM POAOSO (10-69) a N EB s'rsmas PA'ETENT sin Patent No. Dated November 14, l97 2 Iriventofls) Hiroto NAKAMURA It is certified that error appears-s in the above-Mmtificadpotent and that said Letters Paumt are hereby corrected as shown below:

Please insert the following reference to the Japanese Utility Model missing from the original Letters Patent:

Japan, Utility Model Application No. 407'73/69 filed April 24, 1969.

Also correct the filing date of Japanese Patent Application No. 34362/69 as follows:

April 24, 1969.

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.' ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM POJOSO (10-69) 

1. In a picture tube including a periodic electric field-type lens system which comprises at least five metal disks having circular apertures and being axially aligned in sequential order from a first accelerating electrode and along an electron beam path between said first accelerating electrode and a fluorescent screen, the group of disks of odd order being at one potential and the group of disks of even order being at another potential so as to form a periodic electric field along said electron beam path, the improvement in that the apertures of the disks of each said group have the same diameter, the aperture radius r1 of said disks and the distance d between adjacent disks meet the condition 2r1 > OR = d, whereby said disks constitute a unitary main focusing lens system under said periodic electric field to cause electron beams passing through said first accelerating electrode to focus on said fluorescent screen.
 2. A picture tube according to claim 1, wherein the outer radius r2 of said disks, the inner radius r1 of said disks and the distance d between adjacent disks meet the conditions r2-r1 > or = d.
 3. A picture tube according to claim 1, wherein the thickness of each of said disks is less than 0.8 mm. 